Why is the gross margin for customer $2043$ so low? Is it due to low sales or to selling products that have low margins?

Why is the gross margin for customer $2088$ so high? Is it due to a high level of sales or to selling products that have high margins?

If you could choose to advertise a special sale to only special customers, would you advertise to customer $2086$ or to customer $2053?$ Explain.